Add a command line option and a Finch experiment for script streaming.

Script streaming is implemented here: https://codereview.chromium.org/368283002

BUG=

Review URL: https://codereview.chromium.org/547373002

Cr-Commit-Position: refs/heads/master@{#295437}

8 files changed, 15 insertions, 0 deletions

diff --git a/chrome/browser/chrome_browser_field_trials.cc b/chrome/browser/chrome_browser_field_trials.cc
index 4fd69b8..398305e 100644
--- a/chrome/browser/chrome_browser_field_trials.cc
+++ b/chrome/browser/chrome_browser_field_trials.cc
@@ -54,6 +54,7 @@ void ChromeBrowserFieldTrials::InstantiateDynamicTrials() {
   base::FieldTrialList::FindValue("MouseEventPreconnect");
   base::FieldTrialList::FindValue("UnauthorizedPluginInfoBar");
   base::FieldTrialList::FindValue("DisplayList2dCanvas");
+  base::FieldTrialList::FindValue("V8ScriptStreaming");
   // Activate the autocomplete dynamic field trials.
   OmniboxFieldTrial::ActivateDynamicTrials();
 }
diff --git a/content/browser/renderer_host/render_view_host_impl.cc b/content/browser/renderer_host/render_view_host_impl.cc
index 8f497f7..222f263 100644
--- a/content/browser/renderer_host/render_view_host_impl.cc
+++ b/content/browser/renderer_host/render_view_host_impl.cc
@@ -15,6 +15,7 @@
 #include "base/i18n/rtl.h"
 #include "base/json/json_reader.h"
 #include "base/message_loop/message_loop.h"
+#include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
 #include "base/stl_util.h"
 #include "base/strings/string_util.h"
@@ -477,6 +478,10 @@ WebPreferences RenderViewHostImpl::ComputeWebkitPrefs(const GURL& url) {
     }
   }
 
+  prefs.v8_script_streaming_enabled =
+      command_line.HasSwitch(switches::kEnableV8ScriptStreaming) ||
+      base::FieldTrialList::FindFullName("V8ScriptStreaming") == "Enabled";
+
   GetContentClient()->browser()->OverrideWebkitPrefs(this, url, &prefs);
   return prefs;
 }
diff --git a/content/public/common/common_param_traits_macros.h b/content/public/common/common_param_traits_macros.h
index 56b23e4..eede504 100644
--- a/content/public/common/common_param_traits_macros.h
+++ b/content/public/common/common_param_traits_macros.h
@@ -176,6 +176,7 @@ IPC_STRUCT_TRAITS_BEGIN(content::WebPreferences)
   IPC_STRUCT_TRAITS_MEMBER(navigate_on_drag_drop)
   IPC_STRUCT_TRAITS_MEMBER(spatial_navigation_enabled)
   IPC_STRUCT_TRAITS_MEMBER(v8_cache_options)
+  IPC_STRUCT_TRAITS_MEMBER(v8_script_streaming_enabled)
   IPC_STRUCT_TRAITS_MEMBER(pepper_accelerated_video_decode_enabled)
 #if defined(OS_ANDROID)
   IPC_STRUCT_TRAITS_MEMBER(text_autosizing_enabled)
diff --git a/content/public/common/content_switches.cc b/content/public/common/content_switches.cc
index 0fdcfe2..c429372 100644
--- a/content/public/common/content_switches.cc
+++ b/content/public/common/content_switches.cc
@@ -452,6 +452,9 @@ const char kEnableTracingOutput[]           = "enable-tracing-output";
 const char kEnableUserMediaScreenCapturing[] =
     "enable-usermedia-screen-capturing";
 
+// Enables streaming scripts to V8 while loading.
+const char kEnableV8ScriptStreaming[] = "enable-v8-script-streaming";
+
 // Enables the use of the @viewport CSS rule, which allows
 // pages to control aspects of their own layout. This also turns on touch-screen
 // pinch gestures.
diff --git a/content/public/common/content_switches.h b/content/public/common/content_switches.h
index 1c4493c..5196e83 100644
--- a/content/public/common/content_switches.h
+++ b/content/public/common/content_switches.h
@@ -133,6 +133,7 @@ CONTENT_EXPORT extern const char kEnableThreadedCompositing[];
 CONTENT_EXPORT extern const char kEnableTracing[];
 CONTENT_EXPORT extern const char kEnableTracingOutput[];
 CONTENT_EXPORT extern const char kEnableUserMediaScreenCapturing[];
+extern const char kEnableV8ScriptStreaming[];
 CONTENT_EXPORT extern const char kEnableViewport[];
 CONTENT_EXPORT extern const char kEnableViewportMeta[];
 CONTENT_EXPORT extern const char kMainFrameResizesAreOrientationChanges[];
diff --git a/content/public/common/web_preferences.cc b/content/public/common/web_preferences.cc
index d1e656d..32f7987 100644
--- a/content/public/common/web_preferences.cc
+++ b/content/public/common/web_preferences.cc
@@ -136,6 +136,7 @@ WebPreferences::WebPreferences()
       use_solid_color_scrollbars(false),
       navigate_on_drag_drop(true),
       v8_cache_options(V8_CACHE_OPTIONS_OFF),
+      v8_script_streaming_enabled(false),
       cookie_enabled(true),
       pepper_accelerated_video_decode_enabled(false)
 #if defined(OS_ANDROID)
diff --git a/content/public/common/web_preferences.h b/content/public/common/web_preferences.h
index 496a347..b0a95ca 100644
--- a/content/public/common/web_preferences.h
+++ b/content/public/common/web_preferences.h
@@ -142,6 +142,7 @@ struct CONTENT_EXPORT WebPreferences {
   bool use_solid_color_scrollbars;
   bool navigate_on_drag_drop;
   V8CacheOptions v8_cache_options;
+  bool v8_script_streaming_enabled;
 
   // This flags corresponds to a Page's Settings' setCookieEnabled state. It
   // only controls whether or not the "document.cookie" field is properly
diff --git a/content/renderer/render_view_impl.cc b/content/renderer/render_view_impl.cc
index 83ad060..eba0382 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -1069,6 +1069,8 @@ void RenderView::ApplyWebPreferences(const WebPreferences& prefs,
   settings->setV8CacheOptions(
       static_cast<WebSettings::V8CacheOptions>(prefs.v8_cache_options));
 
+  settings->setV8ScriptStreamingEnabled(prefs.v8_script_streaming_enabled);
+
 #if defined(OS_ANDROID)
   settings->setAllowCustomScrollbarInMainFrame(false);
   settings->setTextAutosizingEnabled(prefs.text_autosizing_enabled);